The present invention is directed to image processing technology. More particularly, the invention provides an image processing method and system for detecting changes of an imaged object. Merely by way of example, the invention has been applied to crystallization in a microfluidic device. But it would be recognized that the invention has a much broader range of applicability.
Crystallization is an important technique to the biological and chemical arts. Specifically, a high-quality crystal of a target compound can be analyzed by x-ray diffraction techniques to produce an accurate three-dimensional structure of the target. This three-dimensional structure information can then be utilized to predict functionality and behavior of the target.
In theory, the crystallization process is simple. A target compound in pure form is dissolved in solvent. The chemical environment of the dissolved target material is then altered such that the target is less soluble and reverts to the solid phase in crystalline form. This change in chemical environment is typically accomplished by introducing a crystallizing agent that makes the target material less soluble, although changes in temperature and pressure can also influence solubility of the target material.
In practice however, forming a high quality crystal is generally difficult and sometimes impossible, requiring much trial and error and patience on the part of the researcher. Specifically, the highly complex structure of even simple biological compounds means that they are not amenable to forming a highly ordered crystalline structure. Therefore, a researcher must be patient and methodical, experimenting with a large number of conditions for crystallization, altering parameters such as sample concentration, solvent type, countersolvent type, temperature, and duration in order to obtain a high quality crystal, if in fact a crystal can be obtained at all.
Hansen, et al., describe in PCT publication WO 02/082047, published Oct. 17, 2002 and herein incorporated by reference in its entirety for all purposes and the specific purposes disclosed therein and herein, a high-throughput system for screening conditions for crystallization of target materials, for example, proteins. The system is provided in a microfluidic device wherein an array of metering cells is formed by a multilayer elastomeric manufacturing process. Each metering cell comprises one or more of pairs of opposing chambers, each pair being in fluid communication with the other through an interconnecting microfluidic channel, one chamber containing a protein solution, and the other, opposing chamber, containing a crystallization reagent. Along the channel, a valve is situated to keep the contents of opposing chamber from each other until the valve is opened, thus allowing free interface diffusion to occur between the opposing chambers through the interconnecting microfluidic channel. As the opposing chambers approach equilibrium with respect to crystallization reagent and protein concentrations as free interface diffusion progresses, it is hoped that the protein will, at some point, form a crystal. In preferred embodiments, the microfluidic devices taught by Hansen et al. have arrays of metering cells containing chambers for conducting protein crystallization experiments therein. Use of such arrays in turn provides for high-throughput testing of numerous conditions for protein crystallization which require analysis.
The invention disclosed herein provides systems and methods for conducting such analysis to determine whether a particular set of protein crystallization conditions indeed caused crystals to form.